Effect of enzymatic cross‐linking of milk proteins on properties of ice cream with different composition

Abstract

Transglutaminase enzyme (TGase) treatment has been reported to increase the viscosity of milk and gel stiffness of yoghourt and the treatment has been suggested to replace part of the fat and proteins in dairy products. In this study, the effects of TGase on some physical, rheological and sensory properties of ice cream with different fat and stabiliser contents were studied. Five ice-cream mixes were prepared. Three of them were regular-fat mixes with 10% fat but vary in the stabiliser (0.7% and 0.2%). The other two mixes were low-fat mixes, (5% fat and 0.7% stabiliser), a control and treated sample. The mixes were pasteurised (80°C for 15 min), cooled to 50°C, homogenised (13.8/3.4 MPa) treated with the enzyme (at 45°C for 2.5 h) and aged for 24 h at 5°C before freezing. The viscosity, yield stress and consistency index (k) of all mixes were increased by the TGase treatment. The flow behaviour index (n) of regular-fat mixes changed from non-Newtonian shear thinning (n ¼ 0.9) to non-Newtonian shear thicking or dialtant behaviour (n ¼ 1.26). The flow behaviour index (n) of low-fat mixes did not change by the treatment. On the other hand, the time-viscosity curves at a constant shear rate of all the enzyme-treated mixes have changed from thixotropic to rheopectic (time-thickening) flow. The TGase treated ice creams were superior in all physical and organolyptic properties than their corresponding controls. The enzyme treatment compensated the low-fat or low-stabiliser in the ice cream. Moreover, tailored physical properties of ice cream could be obtained by manipulating the mix-enzyme reaction conditions and amount and type of stabiliser.

Effect of Partial Fat Replacement by Whey Protein, Oat, Wheat Germ and Modified Starch on Sensory Properties, Viscosity and Antioxidant Activity of Reduced Fat Ice Cream

“…Measurements of apparent viscosity of aged ice-cream mixes were carried out according to Metwally [21] with some modifications. Brookfield Programmable Rheometer (Model RVDV-III Ultra; Brookfield Engineering Laboratories, Stoughtm, MA, USA) was used for viscosity measurements.…”

Effect of lactase, transglutaminase and temperature on ice cream crystal by a response surface methodology approach

“…Possibly, a large agglomeration of fat globules, casein micelles, and air bubbles occurs in ice cream studies. Metwally (2007) observed that fat is covered by a partly coalesced protein layer stabilizing the air bubbles and foam structure, which makes for better ice cream texture, avoiding large crystals formation.…”

“…In addition, it is assumed that the performance of transglutaminase formed links between milk proteins, creating a fine network that immobilized the water in large proportions and probably the same occurred with fat to form a firm gel. This causing protein hardening, covering fat globules and taking part in the protein network, creating air bubbles, which occupy spaces in the middle by avoiding water movement as a consequence, hindering large crystals formation observed in ice cream during storage (Metwally, 2007). The crystal formation occurs during the initial freezing process, and its size is critical to determine the ice cream quality.…”

“…The results obtained for crystals content in treatments T1, T3, T5, T7, and T9 (Table 1), show statistically significant differences between the 5% probability level done by the Dunn test (nonparametric). Presumably, transglutaminase performance forming links between milk proteins, creating a fine network that immobilized water in large proportion and probably fat, forming a firm gel caused a protein hardening effect, covering fat globules and taking part in the protein network, creating air bubbles which occupy spaces in the middle and avoiding water movement in the middle (Metwally, 2007).…”

Short communication: Effect of whey protein addition and transglutaminase treatment on the physical and sensory properties of reduced-fat ice cream

“…A 120-g block of ice cream sample was placed on a wire screen located on top of a beaker and allowed to melt at room temperature (22 ± 1°C). The weight of drainage recorded at 10-min intervals was plotted against time and the melting rate (g/min) was calculated from the slope of the melting chart (Elsayed Metwally, 2007).…”